Generally (but far from universally), the elements within a group have similar characteristics. Antimony, nitrogen, and arsenic are all part of the same group as phosphorous (the pnictogens, or group 5A). Oxygen is not in this group, but rather in an adjacent group (the chalcogens, or group 6A). Thus, the answer here should be oxygen.
That said, there can be very significant differences in characteristics among the elements within a group, and that is certainly the case here. For example, free nitrogen exists predominantly as a molecular gas (N₂) and makes up about 78% of the atmosphere we breathe. Elemental arsenic (As), while in the same group as nitrogen, is naturally found in the solid state and is poisonous to humans (arsenic is sometimes included among the toxic heavy metals, although it’s technically a metalloid).
Answer:To convert the model of one constitutional isomer to another constitutional isomer one needs to exchange 2 atoms/groups on different atoms.
To convert the model of one stereoisomer to another stereoisomer one needs to exchange 2 atoms/groups bonded to the same carbon.
To convert the model of one conformational isomer to another conformational isomer one only needs to rotate about single bond(s).
Explanation:
Constitutional isomers differ from each other in position of substituents. Hence if we interchange atoms or groups on two different atoms, we get constitutional isomers.
Stereo isomers posses different orientations in space. If two atoms or groups on the same carbon atoms interchange their spatial orientation, we have a different stereoisomer other than the original structure.
Conformers arise by free rotation across single bonds. Different conformers can be created by rotating single bonds.
The balanced chemical reaction is given as:

Now, convert
into litres.

So, 
Density is equal to the ratio of mass to the volume.

where, M = mass and V= volume 
Substitute the value of density and volume in formula to get the value of mass.



Now, number of moles of
gas=
= 
According to the reaction, 2 moles of sodium azide gives 3 moles of nitrogen gas.
Now, in 24.00 moles of nitrogen gas produced from=
of nitrogen gas, moles of sodium azide.
number of moles of sodium azide = 
Mass of sodium azide in g =
.
= 
= 
Thus, mass of sodium azide which is required to produce
of nitrogen gas = 
Answer:
2HNO3+Ca(OH)2 = Ca(NO3)2+2H2O
Explanation:
The reaction between Nitric acid(HNO3)and Calcium hydroxide(Ca(OH)2) gives Calcium Nitrate( Ca(NO3)2 and Water( H2O)